Driving system for loud speakers



Sept. 20, 1932.

Sept. 20, 1932. H VAN DAM ETAL l 1,878,919

M OR LOUD SPEAKERS Patented Sept. 20, 1932 lUNITED STATES vPATENT? OFFICE HENDRIX vnl' DAI, 02|' CAPELLE-OI-THl-IJBBEL, AND DIRK nmN'UB VAI DAI,

0l' BOTTEBDAI, NETHERLANDS DRIVING SYSTII FOB LOUD SPEAKERS Application lied notober $0, 1080, Serial lo. 490,0, and ln Germany 0otober 8, 1m.

The invention hasY for its object the provision of a driving system for loudspeakers, which is eilicient and easy to manufacture.

The driving system is of the type having a soft iron armature and two or more coils energized by the alternating current, a magnetic field being developed in the armature and in the magnetic material carrying the alternating fluxes of the ,coils by a polarizing magnet characterized in that the armature is shaped as a cylindrical rod and is mounted in and moves in the direction of the common axis of the coils.

According to a feature of the invention the magnetic circuits of the alternati current coils are mutually independent an these circuits are influenced in o posite senses when the armature is Accordingto` another feature of the in'- vention. the armature, coils andpole pieces of the magnet are cylindrical and coaxial with the armature. f i

An fobject if'thleginrenton is the prlpivil; slono a ou s er nving-systemw c is freely suppoprtgd on ball bearings at its extremity and is movable in both directions without being subjected to a restraining force, which might result in a high inherent frequency of the oscillating armature.

Still another object of the invention is a method of constructing ball bearings suitable for this purpose.v According to this method a cylindrical mantle a collar and an inner diameter greater than that of the armature spindle and fitting with its outer diameter in an opening of the housing is bored with a number of longitudinal holes, corresponding to the number of balls whose diameter is smaller than that of the holes. The operation of boring cuts through the outer surfaces of the mantle, so that slits are formed, through which the balls contact with the casing and with the spindle. The borings are afterwards shut of by means' of props.

The invention will be explained in connection with the constructions shown by way of example in the annexed drawings.

Figures 1 and 2 show one form of construction of the driving system according to the invention.

` Figures 3 and 4 show a modified form of construction.

Fi res 5 and 6 show in detail a ball bearing or a driving system according to the invention.

Figure 7 shows a detail.

The driving system accordin 1 and 2 consists of a cylindrical larizing ma et 15 having Two ring s a d alternating current coils 6 and 7 are isposed in casings 4 and 5 placed coaxially within the polarizing magnet. The casin 4 and 5 which surround the coils 6 and on three sides and are to this end constituted by two flat side rings and a circumferential cylindrical rin are constructed of magnetic material an are separated by a distance piece 32 of nonma etic material. The c contact at thelr outward flat surfaces wlth the pole shoes 41 of the permanent magnet.

Inside of the annular casings 4 and 5 the rod-shaped armature v17-21 is mounted in ball bearings 39 fixed inside the pole shoes of the polarizing ma et. The armature consists of a core 21 o non-magnetic material on the middle part of which is clamped a sleeve 17 of magnetic material. This sleeve rests with one end against a ring on the core and is heldin 'tion by a nut 40 to Figures hollow popole shoes 41.

screwed tight against its other end. Thel sleeve 17 is formed with two annular larts at the ends, joined by a thinner sha like portion. The Vannular parts are slightly eater in width than the coils, in which they t with as small a clearance as possible.

Instead of a permanent cylindrical polarizing magnet an electromagnet or a magnet of non-cylindrical form may be used.

Both end surfaces of the apparatus are covered with plates 42, preferable of insulating material.

The coils of the driving system may be connected in series or in parallel.

The ball bearings in which the armature core rests, may be constructed as shown in Figures 5 and 6. According to these figures the main part is a cylindrical mantle 35 hav-v vum ing a collar 37. In this mantle a number of holes 36 is b'ored, forming slits where they pierce the outersurface of the mantle. After introduction of the balls 20 the borings are closed by plugs 38, the slits being so narrow, that the balls cannot fall out. The mantle is now introduced into a central boring of the ole shoe. The balls then contact on the outside with the metal of the pole shoe or with a hardened ring introduced for the purpose and on the inside with a steel ring placed on the armature core in Figures 1 an 2or directly with the armature spindle in Figures 3 and 4.

The armature transmits its movement to a loudspeaker diaphragm or similar apparatus by means of a rod 14 fixed to the armature core.

In operation the polarizing flux flows from one pole of the polarizing magnet through the coil casing and the corresponding annular part of the armature; thence through the armature shaft to the other annular part and the second coil casinff to the other pole. Around every coil this ilux is modified by the speaking currents flowing in the coils in such a way, that north and south poles are generated, which exert attractive and repulsive forces, that tend to move the armature in a longitudinal direction. It should be noted, that the coils should be interconnected in such a way, that the forces exerted on the armature have the same direction for both coils.

When the armature moves, the path followed by the polarizing flux is modified, so

that back electromotive forces are in the coils.

The construction of Figures 3 and 4 differs only from that just described, in that the armature sleeve is mounted on aV spindle of non-ma etic steel 21, thus permitting a reduction 1n diameter and simplifying the construction of the ball bearings.

In all other respects this construction is equal to that of Figures 1 and 2.

According to the modification represented in Figure 7 the inner edges of the sides of the coil casings and the annular partsv of the armature are formed with sharp edges as at 44. Thereby the induction at these points is increased and the electro-mechanical effeet of the driving system is improved. The relative position of the sharp edges of the armature and the coil casings is about the same as that of the square-edges in the other constructions.

It should be clear, that the driving systems may be modified without departing from the principle of the invention.

What we claim is:

1. Driving system for a loudspeaker, comprising an armature of magnetic material, a plurality of driving coils, a casing of magnetic material for each of the coils, a polargenerated and coaxial with the armature an izing magnet in the magnetic circuit of which the armature and the casings of ma etic material surrounding the coils is inc uded, the armature being shaped substantially as a cylinder and beinfg supported slidably in the common axis o the coils the air gaps between the armature and the magnetic material carrying the alternatin fluxes of the coils remainingconstant an the direction of the polarizing flux in the armature being substantially parallel to this axis.

2. Driving system for a loudspeaker, comprising an armature of magnetic material, a plurality of driving coils, a polarizing magnet in the ma etic circuit of which 1s successively inclu ed the fixed magnetic material carrying the alternating flux of one of the coils, the armature and the magnetic material carrying the alternating flux of the other coil, the armature being shaped as a, cylinder and being adapted to slide in the direction of the axis of the coils, the direction of the polarizing flux in the armature being substantially parallel to this axis.

3. Driving system for a loudspeaker comprising an armature of magnetic material, a plurality of driving coils, each havin an enclosing casing of magnetic material aving mutuall independent paths for their alternating uxes, a polarizing magnet in the magnetic circuit of which the armature casings of magnetic material carrying these fluxes are included, the armature, which is substantially cylindrical being supported slidably in the common axis of the coils and adjoining with its respective extremities the pole of the polarizin magnet.

4. 'ving system for a oudspeaker comprising an armature of magnetic material, a pluralit of driving coils, a polarizing magnet in t e magnetic circuit of which is successively included one coil with its fixed magnetic material, the armature and the other coil with its magnetic material, the armature consistin of twov bosses joined by a thinner shaft an being adapted to slide in the direction of the axis, the coilshaving mutually independent paths for their alternating fluxes, the polarizing flux entering the armature at one of the bosses and leaving it at the other.

5. Driving system for a loudspeaker comprising an armature of magnetic material, a plurality of driving coils, a polarizing magnet in the magnetic circuit of which the armature and the coils are included the armature being substantially cylindrical and being supported slidablyvin the common axis of the coils, the coils being c lindrical substan tially of equal size.

6. Driving system for a loudspeaker comprising a soft iron armature, a plurality of driying coils, each having an enclosing iron casing, a polarizing magnet in the magnetic circuit of which the amature and the iron casin of the coils are included, the armature ing substantially cylindrical and being supported slidably in the common axis of the coils, the coils and the pole pieces of the magnet being cylindrical and coaxial with the armature, the polarizing magnet having the form of a cylindrical mantle, and the polarizing field being substantiall of the same shape at both ends of the sai mantle.

7. Driving system for a loudspeaker comprising an armature of magnetic material, arranged at its extremities in ball bearings, a plurality of drivin coils, a polarizing magnet in the magnetic circuit of which the armature and the magnetic material carrying the alternatin fluxes of the coils is included, the armature eing substantially cylindrical and being supported slidably in the common axis of the coils.

8. Apparatus of the class described, comprising a casing forming a magnet and having po e pieces at its opposite ends, an armature arranged in the magnetic casing and mounted for reciprocating longitudinal movement, said armature comprising a nonmagnetic substantially cylindrical core and a ma etic substantially cylindrical sleeve on said core, and a pair of coils through the centers of which the armature extends, said coils having casings of magnetic materi al arranged on the respective pole pieces.

In testimony whereof we have signed oui` names to this s ecification.

HENlgRIK VAN DAM. DIRK HERMANUS VAN DAM. 

